OBJECTIVE: To describe semen quality and reproductive hormone concentrations of young men living in Rochester, New York, and to compare these with published data from similar European and Japanese populations. DESIGN: Cross-sectional study. SETTING: University and college campuses in the Rochester, New York, area. PATIENT(S): Unselected young college students (n = 222). INTERVENTION(S): A physical examination, blood and semen samples, and completion of a brief questionnaire. MAIN OUTCOME MEASURE(S): Semen parameters and serum reproductive hormone levels. RESULT(S): Subjects were aged 18-22 years (median age, 19.5 years), predominantly Caucasian (81%), and nonsmokers (79%), with a mean (SD) body mass index of 25.5 (4.2) kg/m(2). Overall, median sperm concentration was 52 × 10(6)/mL (5th-95th percentiles: 7-181 × 10(6)/mL), median total sperm count was 158 × 10(6) (14-587 × 10(6)), and 23.1% and 15.8% of men had a sperm concentration below 20 × 10(6)/mL and 15 × 10(6)/mL, respectively. Few men had serum hormones falling outside clinically normal ranges. Median sperm concentrations and reproductive hormone levels were comparable to those seen in young men in Denmark, Finland, and Japan. CONCLUSION(S): Our study provides the first data in 70 years on semen quality and reproductive hormones in young men in the United States with unknown fertility. These data suggest that, overall, reproductive parameters in our study population of young college students from the northeastern United States are similar to those of young European and Japanese men.